1. Field of the Invention
This invention relates to means for controlling odors and greenhouse gas emissions from landfills. More particularly, the invention relates to gas flares disposed at capped landfills and adapted to burn landfill gas generated by the decomposition of organic waste.
2. Background Information
As organic waste present in a landfill decomposes, gas commonly known as "landfill gas" is generated. This is a foul smelling gas that generally consists of 55% methane, 44% carbon dioxide and 1% of other various constituents ranging from hydrogen sulfide to complex hydrocarbons. When released directly into the atmosphere, landfill gas may cause severe odor problems. Additionally, methane has been characterized as a "greenhouse" gas which is believed to significantly contribute to global warming.
Currently, once landfills have reached full capacity, they are generally capped with among other things, a layer of topsoil to support vegetation and help prevent erosion. A gas vent, gas well, or other gas collection system is also typically provided to enable the landfill gas generated by the aforementioned decomposition process to conveniently pass through the cap for release.
Because landfill gas burns relatively cleanly, the gas emerging from such a vent, etc. may be burned in an effort to eliminate the aforementioned noxious odor and harmful greenhouse effects. A flare may thus be provided to burn the gas as it emerges from the vent. However, significant disadvantages inhere in this approach which tend to offset the advantages thereof. Particularly, once such a flare has been ignited, it may be difficult to ensure that the flame burns continuously. Several factors contribute to this difficulty, including variations in the flow rate of the gas as a result of environmental conditions such as temperature and ground water levels. Variations in the percentages of the constituents of the landfill gas, namely, methane and CO2, may also affect the optimum gas/air ratio mixture required to maintain a continuous flame. Moreover, adverse weather conditions such as wind and precipitation may tend to extinguish the flame. Because such flares are preferably disposed proximate to the landfill to minimize the use of lengthy gas pipe runs, the flares are usually disposed in remote locations, where it would be difficult to monitor the presence of flame and inconvenient to manually re-ignite the flares in the event the flame is extinguished. Moreover, during any time in which the flame is out, the gas is permitted to escape into the atmosphere, thereby creating potentially lengthy periods in which the odor and greenhouse effects of the landfill are not being treated.
In attempts to remedy this drawback, several devices may be utilized. In particular, vent flares may be provided with electronic ignitors or propane pilot lights. Electronic ignitors generally include sophisticated technology to monitor the presence of flame. In particular, optical or heat sensors may be employed, which, upon detecting an absence of flame, signal electronic circuitry to automatically re-ignite the gas. A drawback of this approach is that such sophisticated equipment is relatively expensive, involving substantial up-front capital expenditure, while also requiring a relatively high degree of routine maintenance.
Propane pilot light systems, on the other hand, help ensure that the landfill gas flame burns continuously by providing a continuously burning pilot light. This type of system has the advantage of being relatively unsophisticated and thus relatively inexpensive to purchase and simple to maintain. A drawback of this approach however, is that the system requires a separate supply of fuel (propane) which must be replaced periodically. In addition, the pilot light itself may be extinguished, by, for example, wind and/or precipitation and thus still require manual re-lighting.
A need therefore exists for an improved landfill gas vent flare that is relatively inexpensive, requires little maintenance, yet serves to reliably maintain a continuous flame under a wide range of operating conditions.